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STUDY DESIGN.: Multicenter, prospective equivalency trial with each patient serving as his/her own control.OBJECTIVES.: To compare the effectiveness of a Grafton® DBM gel composite with iliac crest autograft in posterolateral spine fusion.SUMMARY OF BACKGROUND DATA.: While autograft remains the preferred graft material to facilitate spine fusion, the supply is limited and harvesting produces undesirable clinical consequences.METHODS.: A total of 120 patients underwent posterolateral spine fusion with pedicle screw fixation and bone grafting. Iliac crest autograft was implanted on one side of the spine and a Grafton® DBM/autograft composite was implanted on the contralateral side in the same patient. An independent, blinded reviewer evaluated anteroposterior and lateral flexion-extension radiographs. The fusion mass lateral to the instrumentation on each side was judged fused or not, and the mineralization of the graft was rated absent, mild, moderate, or extensive. The degree of correspondence in outcomes between sides was estimated by computing the percentage agreement and kappa statistic.RESULTS.: Nearly 70% of patients (81 of 120) provided complete 24-month radiographic studies. The bone graft mass was fused in 42 cases (52%) on the Grafton® DBMside and in 44 cases (54%) on the autograft side. The overall percentage agreement for fusion status between sides was approximately 75% (61 of 81), indicating moderately strong statistical correspondence (kappa = 0.51, P < 0.0001). Bone mineralization ratings also were similar between treated sides. Perfect agreement was realized in almost 60% of patients (48 of 81) with moderate statistical correspondence (weighted kappa = 0.54, P < 0.0001).CONCLUSIONS.: Grafton® DBM can extend a smaller quantity of autograft than is normally required to achieve a solid spinal arthrodesis. Consequently, a reduced amount of harvested autograft may be required, potentially diminishing the risk and severity of donor site complications. [ABSTRACT FROM AUTHOR]

STUDY DESIGN.: Retrospective radiographic and chart review. OBJECTIVE.: To examine the relationship between lumbar total disc replacement (TDR) range of motion (ROM) and clinical outcome at 8.6-year follow-up. SUMMARY OF BACKGROUND DATA.: There are no studies on the relationship between TDR motion and clinical outcomes. METHODS.: We reviewed 38 patients who underwent 1 or 2-level TDR implantation with 51 TDR. Flexion-extension ROM was measured on lateral radiographs. Clinical outcomes were measured at 8.6 years by modified Stauffer-Coventry scores, Oswestry Disability Questionnaires (ODQ), and subjective ratings of back pain, leg pain, and disability. Spearman rank correlation coefficient was used to determine if ROM was correlated with clinical outcome. Patients were divided into 2 groups by motion (=5 and >5). Statistical differences in outcome were sought. RESULTS.: Spearman rank correlation coefficient revealed weak-to-moderate but statistically significant associations between ROM and outcome for postoperative back pain (r = -0.35, P = 0.034), ODQ (r = -0.33, P = 0.046), and modified Stauffer-Coventry scores (r = 0.42, P = 0.0095). Patients with motion of >5 had superior outcomes in ODQ (mean difference 12.6 points, P = 0.026) and Stauffer-Coventry scores (mean difference 2.2 points, P = 0.015). CONCLUSIONS.: The radiographic ROM at 8.6-year follow-up was positively correlated with several outcomes measures. Patients with motion >5 had clinically modest but statistically better outcomes in ODQ and modifiedStauffer-Coventry scores. Longer follow-ups will be necessary to measure fully the impact of TDR ROM on outcome. [ABSTRACT FROM AUTHOR]

SUMMARY: The rationale for total disc replacement is avoidance of the junctional degeneration seen after arthrodesis by preservation of segmental motion. To justify the use of disc prostheses, it is essential to document maintained range of motion (ROM) and sagittal alignment at long-term follow-up. This is a retrospective radiographic study of 42 patients who had placement of 58 first-generation Prodisc prostheses at a mean follow-up of 8.7 years. Flexion-extension ROM was measured by Cobb's method. Junctional levels were evaluated for junctional degeneration. Pre- and postoperative global and segmental lordosis were measured. Prognostic patient factors predicting ROM of <2° were evaluated. We observed ROM of at least 2° in 66% of Prodisc prostheses at 8.7-year follow-up, although ROM was less than that reported in asymptomatic normal individuals. Mean ROM for disc prostheses with motion was 7.5° at L3-L4, 6.2° at L4-L5, and 4.1° at L5-S1. Mean ROM for all prostheses was 3.8°. The incidence of radiographic junctional degeneration was 24%, although no patients required surgery for symptomatic junctional degeneration. Mean ROM of prostheses below a degenerated junctional disc was 1.6° compared with 4.7° below a normal junctional disc (P < 0.035). Females were 3.5 times more likely to have ROM of <2°. This is the longest published follow-up study of a lumbar disc replacement. The data show that ROM is preserved at long-term follow-up in the majority of patients. Global and segmental sagittal alignment improve after surgery. Furthermore, there is an association between ROM of disc prostheses and the development of junctional degeneration. [ABSTRACT FROM AUTHOR]

Lumbar total disc replacement (TDR) is an evolving technique that has the potential to replace arthrodesis as the gold standard surgical treatment of degenerative disc disease. The interaction between host anatomy and physiology and the biomechanical properties of TDR implants will determine the quality of long-term clinical results. However, there is scant literature addressing this subject. The purpose of this article is to discuss the implications of biomechanical constraint in TDR. Based upon available data for normal motion segments and the design of two TDRs currently in clinical trials, unconstrained designs appear to have a kinematic advantage. They are more likely to provide a physiologic mobile instantaneous axis of rotation (IAR), which may explain why they display greater range of motion in vivo. Their lack of constraint may prevent excessive facet joint or capsuloligamentous loads in the extremes of flexion and extension. Furthermore, since the IAR is mobile, they may be less sensitive to small errors in implant placement. On the other hand, constrained devices appear to have an advantage in protection of the posterior elements from shear loading. Spinal shear loads of considerable magnitude occur during activities of daily living. Whether the transference of stresses to the implant and implant-bone interface is clinically significant is unknown. Although this article focuses on two specific TDR designs, future designs will need to account for the same kinematic and loading concerns regarding constraint. We hope this discussion will assist clinicians and researchers in the design, selection, and clinical comparison of present and future TDR implants. [ABSTRACT FROM AUTHOR]

Lumbar total disc replacement (TDR) is an evolving technique that has the potential to replace arthrodesis as the gold standard surgical treatment of degenerative disc disease. The interaction between host anatomy and physiology and the biomechanical properties of TDR implants will determine the quality of long-term clinical results. However, there is scant literature addressing this subject. The purpose of this article is to discuss the implications of biomechanical constraint in TDR. Based upon available data for normal motion segments and the design of two TDRs currently in clinical trials, unconstrained designs appear to have a kinematic advantage. They are more likely to provide a physiologic mobile instantaneous axis of rotation (IAR), which may explain why they display greater range of motion in vivo. Their lack of constraint may prevent excessive facet joint or capsuloligamentous loads in the extremes of flexion and extension. Furthermore, since the IAR is mobile, they may be less sensitive to small errors in implant placement. On the other hand, constrained devices appear to have an advantage in protection of the posterior elements from shear loading. Spinal shear loads of considerable magnitude occur during activities of daily living. Whether the transference of stresses to the implant and implant-bone interface is clinically significant is unknown. Although this article focuses on two specific TDR designs, future designs will need to account for the same kinematic and loading concerns regarding constraint. We hope this discussion will assist clinicians and researchers in the design, selection, and clinical comparison of present and future TDR implants. [ABSTRACT FROM AUTHOR]

STUDY DESIGN.: This is a retrospective review of the epidemiology of contraindications to lumbar total disc replacement (TDR). OBJECTIVE.: To define the prevalence of contraindications to lumbar total disc replacement in a cohort of patients undergoing lumbar surgery in the senior authors (F.P.C.) practice. SUMMARY OF BACKGROUND DATA.: No published reports have documented the prevalence of contraindications to lumbar total disc replacement. METHODS.: We performed a retrospective review of 100 consecutive patients who had lumbar surgery by one surgeon between September and December 2002. Procedures performed and contraindications to TDR were recorded. Contraindications to TDR included central or lateral recess stenosis, facet arthrosis, spondylolysis or spondylolisthesis, herniated nucleus pulposus with radiculopathy, scoliosis, osteoporosis, and postsurgical pseudarthrosis or deficiency of posterior elements. Patients were divided into fusion and nonfusion groups. The percentage of patients without contraindications to TDR was calculated. RESULTS.: Of 100 patients, 56 had fusions and 44 had nonfusion surgery. In the fusion group, 56 of 56 patients had contraindications to TDR. In the nonfusion group, 11% (5 of 44) were candidates for TDR. Overall, 5% of patients in this series were candidates for TDR. The average number of contraindications to TDR was 2.48 (range, 05). CONCLUSIONS.: Predictions that TDR will replace fusion are premature. A small percentage (5%) of the patients currently indicated for lumbar surgery at our institution have no contraindications to TDR. Future growth in TDR implantation will result from the indication of patients for surgery who would not be indicated today or from the elimination of current contraindications. [ABSTRACT FROM AUTHOR]

This is a retrospective review of 32 patients with multilevel cervical myelopathy treated by laminectomy and lateral mass plate fusion. The prognosis of surgically treated myelopathy is evaluated as well as prognostic factors for recovery of myelopathy. Diagnoses included cervical spondylosis or ossification of the posterior longitudinal ligament. Final follow-up was at 15.2 months (mean) postoperatively. Myelopathy was graded preoperatively and postoperatively by the system of Nurick. All patients had preoperative radiographs and magnetic resonance imaging (MRI). The presence of abnormal T2-weighted MRI signal (myelomalacia) was noted. Postoperative studies included flexion-extension radiographs to assess fusion and MRI to evaluate decompression of neural elements and resolution of myelomalacia. Severity of preoperative Nurick myelopathy, presence of myelomalacia, and age were evaluated as potential prognostic indicators for surgically treated myelopathy. Mean Nurick score improved from 2.6 (range 1-4) to 1.8 (range 0-3) postoperatively (p < 0.0001). Twenty-two patients (71%) had improvement in Nurick grade of at least one point, and nine showed no improvement. No patients had deterioration of Nurick grade. Preoperative myelomalacia was noted in 15 (47%) patients, and all 15 had residual myelomalacia postoperatively. Severe myelopathy, age, and myelomalacia had no prognostic value for improvement of myelopathy. Complications included pseudarthrosis (3%), wound infection (9%), and transient C5 palsy (6%). This study demonstrates excellent outcomes from laminectomy and fusion in multilevel cervical myelopathy. A high rate of improvement of myelopathy was observed, neurologic deterioration did not occur, and complication rates were low. Severe myelopathy and myelomalacia on preoperative MRI had no prognostic value. [ABSTRACT FROM AUTHOR]